Oscar winner Jennifer Connelly is reeling from a broken heart — and the culprit is lady slayer Russell Crowe.

Just before what should have been the greatest night of her life, Jennifer’s happiness was shattered. Her boyfriend — former “Sports Night” star Josh Charles — dumped her in a jealous rage over her handsome co-star in “A Beautiful Mind.”

Fans and movie critics remarked how down the actress seemed the night she walked off with her Academy Award — and The ENQUIRER’s discovered the secret behind her ongoing sadness.

“Even though Russell and Jennifer were nothing more than friends, her boyfriend Josh saw red when Russell presented her with a vintage car for a gift for her wonderful performance,” revealed an insider.

“Russell and Jennifer became good friends during the filming — and nothing more.

“But the image of their steamy love scenes drove Josh over the deep end. After the movie came out, he nagged Jennifer night and day over his suspicions of a romance.

“Jennifer tried her best to explain that she and Russell were nothing but pals. But Josh was never really convinced. Making things worse, Russell surprised Jennifer with a mint condition 1979 Buick as a gesture of appreciation for her good work. Josh blew a gasket!

“Jennifer and Josh began fighting night and day — and finally he dumped her just days before the Oscars.

“What should have been the happiest day of Jennifer’s life was the most miserable.”

Before the Oscars, Crowe gave interviews praising Jennifer’s magnificent performance — and his present of the car underscored his appreciation, said a close source.

“But Josh was so jealous he would not let Jennifer drive the car. It’s just been sitting in her garage for months!

“It didn’t help that everyone knew that Russell had surprised Meg Ryan with a similar classic car back when they were dating.”

Since the breakup, Jennifer’s become very insecure, revealed the insider. “She’s even had her wardrobe people worried sick because she started saying she was getting heavy.

“The woman is a size three and still thinks she’s fat. An Oscar hasn’t brought her happiness.”